JPH01126057A - Transmission method and transmission system - Google Patents

Abstract

PURPOSE:To send a picture signal and a voice signal simultaneously in two directions by providing a filter to terminal stations connected by a voice band transmission line, dividing a prescribed frequency based on a reference frequency so as to form a frequency for a picture signal and that for a voice signal. CONSTITUTION:Frequencies 300Hz-3.4kHz for voice band are divided at the frequency of 2kHz, and the frequency of 300Hz-1.5kHz is used for a voice signal and the frequency of 2-3.4kHz is used for a picture signal. A picture inputted from a camera CA at the equipment A is stored, modulated and sent to a transmission/reception signal separation section 5a via an HPF 1a. The voice input is sent to a separation section Sa via an LPF 3a. The picture signal sent from the equipment B via the line L to the separation section Sa is given to an HPF 2a, demodulated and stored and then outputted to a picture output section and the voice signal is given to an LPF 4a and outputted to the voice output section. The separation section Sa, Sb of the equipments A, B are connected by a telephone line L and the equipment B acts like the equipment A similarly. Thus, the simultaneous transmission/reception of the picture and voice is executed with a low cost and the system is made suitable for television telephone system.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a transmission method and a transmission system used in a video telephone.

(Prior Art) Conventional videophones using telephone lines can make calls on both sides at the same time, but cannot transmit and receive image data in one direction at the same time. For this reason, if you want to send an image from one side during a call, interrupt the call, switch the image forwarding button, send the image, and after the receiving side receives it, switch. The reality was that they were talking on the phone again.

(Problems to be Solved by the Invention) According to the conventional example, it is not possible to talk while transmitting an image while both parties are viewing the image, and it is not possible to conduct a video conference using a normal telephone line, for example. I needed to.

An object of the present invention is to keep equipment costs low and to enable both parties to talk while viewing the image by using a transmission line whose main purpose is to send audio signals, such as a telephone line. .

(Means for Solving the Problems) The transmission method of the present invention filters the image frequency part and the audio frequency part in the frequency range of a transmission path where the maximum band can pass an audio signal, such as a telephone line. (1a, 2a, 1
b, 2b) (3a, 4a.

3b, 4b), the image signal and audio signal from the A side and the B side are simultaneously transmitted to the other side through the same transmission path by dividing based on a predetermined frequency, and the transmission/reception separation unit transmits the signal from the own station. This separates the reception from the other party.

The transmission system of the present invention has an image input side (A1.81), an image output side (A2°B2), an audio input side (A3.B3), and an audio output side (A4.B4) on both the A and B sides. Both sides use the same transmission path, and the image input side is equipped with an image input section, a storage section, a modulation section, and image signal filters (1a, 1b) connected to the transmission path, and an image output side. The side is equipped with a storage section, a demodulation section, and an image signal filter (2a, 2b) connected to a transmission path, and the audio input side and output side are respectively equipped with an audio input section, an audio output section, and an audio signal filter. (3a, 3b, 4a.

4b), and the A-side and B-side filters are connected by the transmission path via the transmission/reception signal separation section.

(Example) The present invention will be explained in detail below.

The frequency bandwidth currently adopted as an international telephone standard is 300 Hz to 3.4 kHz, and Japan's telephone system is based on this.

In the present invention, this frequency range is divided into two by a filter into a high frequency part and a low frequency part using 2 kHz as a division point.

The higher the frequency, the higher the clarity of the call, but at the same time the frequency division point is limited by the frequency range occupied by the image signal in order to transmit image data. For this purpose, the occupied frequency band of the signal for sending image data is set at 2kHz to 3.4kHz, with 2kHz as the division point.
Then, 991 points are 2kHz. Considering the characteristics of the filter, the occupied frequency band for telephone calls is set to 300Hz to 1.
Use as 5kHz. The signal for image data is SSB (Single 5ide) using the upper sideband.
3and), data transmission of 4 bits (16 gradations) is performed. By doing so, since the frequency ranges used are different, image data can be transmitted or received at the same time while making a two-way call at the same time.

In Figure 1, the image input side A1 on the A side, the image output side A
2 and the image input side on the B side! 31, each filter 1a, 2a, 1b, 2b indicates a 2kHz high-pass filter (HPF) with the image output side B2, the audio input side on the A and B sides, and the output side A3. A4. Each filter 3a, 4 of B3°B4
a, 3b, 4b are 2kHz low pass filters (LPF)
shows. A transmitting/receiving signal separating section is provided on the A and B sides, one separating section is connected to the filters 18 to 4a on the A side, and the other separating section is connected to the filters 1b to 4b on the B side, and both female sections are connected to one telephone line. connected with.

Therefore, first, a transmission method from the A side (outside the figure) to the B side (right side) will be explained together with the system.

When sending image data from the A side to the B side, the image is transmitted by the image input unit (camera) CA, and after first storing the data in the storage unit, this data is modulated by the modulation unit, and the data is modulated at 2kHz.
z~3.4kHz signal is transmitted to the B side.

The signal sent from side A to side B through the telephone line is
Since the frequency band is from 2kHz to 3.4kHz, it passes only through the high-pass filter 2b, is demodulated by the demodulator, and -
The image is stored in the storage unit, and then transferred to the image output unit (TV, etc.) M.
By sending the image at a speed suitable for 2S, the image input section C
The image taken at A is displayed on the output section MB.

When a conversation occurs while transmitting or receiving image data, for example, when there is a voice input to the A-side sound weight input section (telephone, etc.),
The audio input signal is passed through the low-pass filter 3a to 1.5
Only the components below kHz are extracted and transmitted to the B side through the telephone line.

At this time, since this signal can only pass through the low-pass filter 4b, it is output to the audio output unit (such as a telephone receiver) without affecting the image data signal. vice versa,
Since the image data signal from the A side cannot pass through the filter 4b, it does not affect the telephone call.

When transmitting image data from the B side to the A side, the transmission method is substantially the same, just in the opposite direction to the above-mentioned direction.

The signal sent from the A side and the signal sent from the B side via the telephone line are separated in the separation section, so the A side.

When image data signals are sent from the B side at the same time, the data signals sent from the A side can only be received by the B side, and the same applies to audio signals. In this way, simultaneous two-way transmission and reception of image data and phone calls can be performed.

Here, the transmission/reception signal separation section will be explained.

This separation section is for preventing loopbacks in which, for example, a signal sent from the input section of the A side is received by the output section of the A side, and separating the signal sent by itself from the signal from the other side. . The circuit configuration of the separation section is shown in Figure 2 (A) to (C).
and shown in FIGS. 3(a) to (d).

In the example shown in FIG. 2, an impedance change characteristic ZB corresponding to the impedance change on the right side with point A as the center within a certain band is configured, and the wraparound is prevented by maintaining balance as a bridge circuit.

In the example shown in the third diagram, ZB, ZBI, ZB2.
Bridge balance is achieved by connecting ZB and setting ZB so that even if point A is the center, the impedance on the side can be regarded as a pure resistance (constant value).

Here, the transmission method will be further briefly explained with reference to the circuit diagram shown in FIG.

In advance, use the terminals LIA and L2A for one line of the telephone line and switch the switches 5W-B-1 and 5W-8-2 to 1". Also, the inverter circuit 5 on the upper side (not shown)
A square wave excavator of Hz is configured, and this is used as the reference oscillation frequency. The frequency of this 8kHz7 is divided by 1z2 by the flip-flop circuit 6 to 4kHz, which is input by an image input section (camera) and used as a clock signal when reading data in the memory as 4-bit data. This is further frequency-divided by 1z2 to form a 2kHz square wave, which is then converted into a sine wave by the LG resonance circuit 7 tuned to 21<@z, and this is used as a carrier wave. This sine wave is amplified to a specified level by the amplifier circuit 71 and then input to the four analog switches 8. This analog switch is turned on and off by the 4-bit image data read out by the clock signal described above.

For the image data input from the image input section (D1 to D4) (upper side outside the figure), one data (4 bits) is read out from the storage section every cycle in synchronization with the carrier wave, and the image data corresponding to this data is read out from the storage section in synchronization with the carrier wave. , the four analog switches 8 are turned on and off. Since this analog switch has weights corresponding to each bit, 16 levels of amplitude modulation are performed based on the data. When all the data is "L11", in order to prevent the carrier from becoming zero, the r of the switch circuit 8 is
16RJ (upper side of the figure) has been added. The occupied frequency band of the image signal modulated by this circuit is 2kHz±
1 kHz (1 kHz to 3 kHz), this modulated wave is first converted to a 3.4 kt-1z LPF Al
When the modulated wave is passed through a 2kHz2HPF1a2°1kHzBEF (band rejection filter) 1a3, only the upper sideband can be extracted from the modulated wave. A signal in this occupied frequency band of 2 kHz to 3 kHz can be used as a signal for image data. The image data signal is a hybrid (H
The signal is transmitted from the amplifier TX of the YB) circuit to the telephone line via the transformer and LIA.

In addition, the audio signal input from the transmitter (audio input section) 9 is amplified by MICAMP and then converted to 1.5kHz LP.
F3a1.2kHzBEF3a2 and BEF (not shown).

) at the output of the C and HYB (hybrid) circuits, the occupied frequency band 30
A signal of 0Hz to 1°5kHz is used as an audio signal. The audio signal is transmitted from the amplifier TX of the HYB (hybrid) circuit to the telephone line via the transformer and L2A at the same time as the image signal.

Further, the image signal and the audio signal transmitted simultaneously through the telephone line pass through the transformer 5W-8-2, the amplifier RX of the HYB circuit, and are separated into the image signal and the audio signal by a filter.

That is, the image data signal is 3.4kHz2LPF2b
The audio signal component is removed by passing it through the 1.2kHz HPF2b2.1kHzBEF2b3 and only the image data signal is extracted.
-11 is input.

This analog switch is turned on and off by locking the PLL circuit at the carrier wave (>2 kHz) included in the image data signal and creating a sampling pulse whose phase and frequency match the carrier wave.The output of the analog switch There is a hold capacitor C8H on the side, and it will be in a hold state until the next sampling is performed.The reason why sampling and holding is performed here is that this method is effective against telephone line noise, etc. This sampled and held image signal is input to a 4-bit AD converter after passing through the buffer amplifier 12. As the clock for this AD converter, the CO output of the PLL circuit described above is used for sampling. , and demodulates 4-bit data.When writing this data into the storage section, stable writing can be achieved by using the vCO output of the PLL circuit as the clock.

Also, the audio signal is 1.5kHz2LPF4b1 and 2kHz
By passing through the BEF4b2, only the audio (call) component (300 Hz to 1.5 kHz) other than the image signal is output from the receiver (audio output section>10).

At the time when the handset 10 is lifted, the user may have picked up the handset after receiving a ring signal (when receiving a call). When lifted, the voltage at point "F" (center on the right side of the figure) in the circuit is 'L'. If this is not the case, it is detected that it is "H19", the initial state of the flip-flop 13 (fixed) is determined, and the initial operation at the time of oscillation or reception, or the control at the time of reception inversion is thereby performed.

The dividing point is not limited to the upper 2kt-(z) as long as the range of the band below the dividing point allows the voice to be heard clearly.

Instead of each of the above pass filters (HPF, LPF), a band pass filter (BPF) may be used, and in this case, the filters 1a, 2a, 1b, and 2b have a frequency of 2kHz to 3.0kHz.
It is assumed that the filters 3a, 4a, 3b, and 4b are 2kHz to 3.4kHz2BPF.

The videophone may be cordless. The 4-4 structure of the transmission line is not limited to metal, and may be an optical fiber cable or the like. It goes without saying that the present invention can also be used in car telephones. Furthermore, as long as the transmission path is used for the main purpose of transmitting audio signals, the transmission path is not limited to telephone lines, but can also be applied to amateur radio, personal radio, etc., and as long as audio and images can be transmitted simultaneously, the transmission path is It doesn't matter if it's wired or wireless.

(Effects of the Invention) According to the present invention, image data and audio can be transmitted and received simultaneously in both directions over a single line using a transmission line whose main purpose is to send audio signals, such as a telephone line. , equipment costs are kept low, both parties can talk while viewing the image, and it is useful for video conferences and the like.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIGS. 2 and 3 are circuit diagrams of a transmitting/receiving signal separating section, and FIG. 4 is a circuit diagram. 1a to 4a, 1b to 4b...filter, A1. B1・
...Image input side, A2. B2...image output side, A3. B3...audio input side, A4.84...audio output side, CA, CB...image input section, MA, MB...image output section. Applicant for the above patents: Mucom Co., Ltd. Figure 2 (A) (B) (C)

Claims (1)

[Claims] 1. Filters (1a, 2a, 1b, 2b) (3a, 4a, 3
b, 4b), the image signal and the audio signal from the A side and the B side are simultaneously transmitted from one side to the other side through the same transmission path, and the transmitting and receiving signals are separated by the transmitting and receiving separation section. Characteristic transmission method. 2. The transmission method according to claim 1, wherein the transmission path is a telephone line. 3. Both A and B sides have an image input side (A1, B1), an image output side (A2, B2), an audio input side (A3, B3), and an audio output side (A4, B4), and both sides are the same. The transmission path is a transmission path, and the image input side includes an image input section, a storage section, a modulation section, and image signal filters (1a, 1b) connected to the transmission path.
The image output side is equipped with a storage unit, a demodulation unit, and image signal filters (2a, 2b) connected to the transmission line, and the audio input side and output side are respectively equipped with an audio input unit and an audio output unit. part, audio signal filter (3a, 3b, 4a, 4
A transmission system comprising (b), wherein the A-side and B-side filters are connected by the transmission path via a transmitting/receiving signal separating section.